These are both ways of
translating High level
languages into lower level
ones
A compiler checks and
translates the whole of
the source code before
running the program
An interpreter translates
and executes the souce
code a chunk at a time. It
translates a line then runs
it
Example
Python is an iterpreted
language because it is
executed by an interpreter
There are two ways to use this interpreter: Interactive mode and
Script mode. Interactive mode is on the initail window marked
by >>> which is a direct way to execute code >>> 2+2 and python will
respond on the next line with >>> 4 . Script mode needs a new
window opened and is used for larger and more demanding
scripts like a full game or etcha-sketch
High Level and low level
programs
Higher level programs
are able to work on a
variety of computers
with very little
tweaking
Python is a high level
program so the
computer has to go
through it before it runs.
Other examples are Java
and C++
Low level programs
don't need
translating
1.2
What is a program?
A program is a set of
instructions that says how to
perform a computation
The details vary per specific language but same basic
principals remain. These are what a program is translated
into, it doesn't matter how complicated it may be
Input: Gathering data from a keyboard,
mic or other device
Output: Displaying the data on a screen
or other device
Math: Simple addition,
subtraction etc
Conditional execution: Looking for the
IFs and BUTs within a program and
following them
Repetition: Repeating an action.
sometimes with slight variations
1.3
Debugging
Debugging is the process of finding
and correcting errors in you program
There are 3 types of error
Syntax Error
A syntax error is an error with the rules
of a structure: (2+2) is legal, but 2+2) is
not because brackets always come in
pairs
Runtime Error
Runtime error is an
error that occurs after
the program has
started running
Semantic Error
A semantic error is not a problem with
how you composed the program's
structure it is a problem with what you
wanted the program to do: so you
wanted to print "Hello" but you typed
print "Helo" instead that would be a
semantic error
1.4
Language types
Formal
These were created to
express a point in a clear and
easily understood way
Examples of this
are mathematical
notation and
chemical short
hand
Maths has basic
syntax rules: 2+2 = 4 is
correct but 3+=4(0 isn't
Chemical short hand also has basic
syntax rules: CO is the short hand for
carbon monoxide but Zz doesn't work
as there is no element with the short
hand of Zz
Natural
These are languages like
English, German and
French, they have evolved
over time, they were NOT
created over night or by
one specific person
1.5
The first program
The traditional first
program you should write
is, in python: print "Hello,
World" , this is a print
statement meaning it will
show Hello, World on the
screen. the " in the program
defines what will be
displayed and the print is
the output method
1.6
Treating the computer right
Many people treat a computer as though
it was a real person, getting angry at it
when it points out the smallest fault and
viewing it as a teammate when it all
seems to be going well.
The best way to view a computer is to see it as a fellow student that
has certain strengths and weaknesses: it is efficient, fast and hard
working but it is pedantic and narrow minded. try to use the
advantages and work around the weaknesses to get the best from
your computer